Abstract:

The electrodeionization process (EDI)with frequent polarity reversal, consisting of dilute and concentrate compartments both filled by ion-exchange resins, was developed to avert the difficult problem of deposit of metal hydroxide in treating heavy metal ions-containing solution.With feed of dilute NiSO4 solution, using operation processing: partial circulation of concentrate stream and successive switching of dilute and concentrate streams, both the high retention rate of desalination water and high concentrating ratio of concentrated product water were achieved just in a single process of EDIR.The best separation could be attained when the period of polarity reversal was 4 h.For NiSO4 solution feed containing 50 mg·L^-1 Ni ²⁺ and pH of 3.0, the Ni ²⁺ concentration in exit dilute and concentrate streams could reach 1.5 mg·L^-1 and 3961 mg·L^-1, and the efficiency of Ni ²⁺ removal was 97% and the concentrating ratio 79.2, respectively, approaching theoretical value.In the experimental range, the EDIR process could be operated with good stability and without Ni (OH)₂ deposit.

Key words:

电去离子, 倒极, 镍离子, 重金属

摘要：

通过在电去离子（EDI）的淡化室和浓缩室中同时填充离子交换树脂而构成频繁倒极电去离子（EDIR）过程，用以解决处理含重金属离子溶液时EDI内部易产生金属氢氧化物结垢的关键难题。以NiSO₄溶液为处理对象，采用浓缩水部分循环和浓、淡水流分步切换的运行工艺，利用EDIR单一过程，同步获得了淡化出水的高截留率和浓缩产品水的高浓缩倍数。实验条件下，倒极周期为4 h可获最佳分离效果。对于含Ni ²⁺ 50 mg·L^-1、pH为3.0的NiSO₄溶液，EDIR的淡水出水和浓水出水的Ni ²⁺浓度可分别达到1.5 mg·L^-1和3961 mg·L^-1，淡水中Ni ²⁺的脱除率为97%，浓水的浓缩倍数则为79.2，接近理论值。实验范围内，EDIR过程运行稳定，未产生Ni(OH)₂结垢。

关键词:

电去离子, 倒极, 镍离子, 重金属